Electron paramagnetic resonance characterization and conformation of daunorubicin semiquinone intermediate implicated in anthracycline metabolism, cardiotoxicity, and anticancer action

1981 ◽  
Vol 59 (22) ◽  
pp. 3212-3217 ◽  
Author(s):  
J. William Lown ◽  
Hsiao-Hsiung Chen
Keyword(s):  
Aqueous Solution ◽  
Antitumor Antibiotic ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Acetyl Group ◽  
G Value ◽  
The Individual ◽  
Electron Paramagnetic ◽  
Spin Densities ◽  
Good Agreement

The antitumor antibiotic daunorubicin, upon reduction in aqueous solution, gives a transient resolved epr spectrum of linewidth 17.0 G and g value of 2.0024. This is ascribed to the semiquinone previously tentatively assigned in the unresolved epr spectrum obtained by microsomal activation of the antibiotic. By reference to the epr spectrum of quinizarin semiquinone in aqueous solution the individual proton hyperfine splitting constants in both spectra were tentatively assigned by computer simulation. LCAO–MO calculations of one-electron wave function spin densities in both species gave good agreement between calculated and observed hfs for values of the parameters βCO/βCC = 1.8, δα = 1.4, allowing definite assignment of the aromatic protons. By considering the angular dependence of the ring A benzylic proton hfs it was possible to discriminate between two alternative half-chair conformations of daunorubicin semiquinone. The preferred conformation of the intermediate is tentatively assigned as that which places both 7 and 9 oxygen functions equatorial and the C-9 acetyl group axial.

Investigations of the Gyromagnetic Factors for the Ni3+ Center in MgO

2010 ◽  
Vol 303-304 ◽  
pp. 113-116
Author(s):  
Xue Mei Li
Keyword(s):  
Local Structure ◽  
Relative Elongation ◽  
Impurity Center ◽  
Theoretical Calculations ◽  
Paramagnetic Resonance ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
G Value ◽  
Electron Paramagnetic ◽  
Good Agreement

The electron paramagnetic resonance (EPR) gyromagnetic factors for the Ni3+ center in MgO are theoretically investigated using the improved g formulas for a tetragonally elongated octahedral 3d7 complex suffering the dynamical Jahn-Teller effect. From the studies, the impurity Ni3+ center is found to undergo the relative elongation along the tetragonal axis by about 1%. The calculated g value shows good agreement with the observed result, and the improvement in the theoretical calculations is achieved in this work as compared with the previous treatments. The local structure of the impurity center is discussed.

Temperature Dependent Line-Shape of the Silicon Dangling Bond EPR-Resonance in Polycrystalline Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
N. H. Nickel ◽  
E. A. Schiff
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Polycrystalline Silicon ◽  
Room Temperature ◽  
Dangling Bond ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Temperature Electron ◽  
Motional Narrowing ◽  
G Value ◽  
Electron Paramagnetic

AbstractThe temperature dependence of the silicon dangling-bond resonance in polycrystalline (poly-Si) and amorphous silicon (a-Si:H) was measured. At room temperature, electron paramagnetic resonance (EPR) measurements reveal an isotropie g-value of 2.0055 and a line width of 6.5 and 6.1 G for Si dangling-bonds in a-Si:H and poly-Si, respectively. In both materials spin density and g-value are independent of temperature. While in a-Si:H the width of the resonance did not change with temperature, poly-Si exhibits a remarkable T dependence of ΔHpp. In unpassivated poly-Si a pronounced decrease of ΔHpp is observed for temperatures above 300 K. At 384 K ΔHpp reaches a minimum of 5.1 G, then increases to 6.1 G at 460 K, and eventually decreases to 4.6 G at 530 K. In hydrogenated poly-Si ΔHpp decreases monotonically above 425 K. The decrease of ΔHpp is attributed to electron hopping causing motional narrowing. An average hopping distance of 15 and 17.5 Å was estimated for unhydrogenated and H passivated poly-Si, respectively.

Studies of local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) crystals

2021 ◽  
Vol 76 (4) ◽  
pp. 299-304
Author(s):  
Fu Chen ◽  
Jian-Rong Yang ◽  
Zi-Fa Zhou
Keyword(s):  
Crystal Field ◽  
Elongation Ratio ◽  
Paramagnetic Resonance ◽  
Local Structures ◽  
Epr Parameters ◽  
Structure Constants ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
Theoretical Results ◽  
Good Agreement

Abstract The electron paramagnetic resonance (EPR) parameters (g factor g i , and hyperfine structure constants A i , with i = x, y, z) and local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) are theoretically investigated using the high order perturbation formulas of these EPR parameters for a 3d 9 ion under orthorhombically elongated octahedra. In the calculations, contribution to these EPR parameters due to the admixture of d-orbitals in the ground state wave function of the Cu2+ ion are taken into account based on the cluster approach, and the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the studied EPR parameters with the local structures of the Cu2+ centers. Based on the calculations, the Cu–H2O bonds are found to suffer the axial elongation ratio δ of about 3 and 2.9% along the z-axis, meanwhile, the planar bond lengths may experience variation ratio τ (≈3.8 and 1%) along x- and y-axis for Cu2+ center in (NH4)2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O, respectively. The theoretical results show good agreement with the observed values.

Evaluation of systemic blood NO dynamics by EPR spectroscopy: HbNO as an endogenous index of NO

2003 ◽  
Vol 285 (2) ◽  
pp. H589-H596 ◽  
Author(s):  
Kazuyoshi Kirima ◽  
Koichiro Tsuchiya ◽  
Hiroyoshi Sei ◽  
Toyoshi Hasegawa ◽  
Michiyo Shikishima ◽  
...  
Keyword(s):  
Endothelial Dysfunction ◽  
Whole Blood ◽  
Computer Assisted ◽  
Subtraction Method ◽  
Epr Spectrum ◽  
Systemic Blood ◽  
Paramagnetic Resonance ◽  
Species Overlap ◽  
Epr Signal ◽  
Electron Paramagnetic

The measurement of hemoglobin-nitric oxide (NO) adduct (HbNO) in whole blood by the electron paramagnetic resonance (EPR) method seems relevant for the assessment of systemic NO levels. However, ceruloplasmin and unknown radical species overlap the same magnetic field as that of HbNO. To reveal the EPR spectrum of HbNO, we then introduced the EPR signal subtraction method, which is based on the computer-assisted subtraction of the digitized EPR spectrum of HbNO-depleted blood from that of sample blood using the software. Rats were treated with Nω-nitro-l-arginine methyl ester (l-NAME; 120 mg · kg–1 · day–1) for 1 wk to obtain HbNO-depleted blood. When this method was applied to the analysis of untreated fresh whole blood, the five-coordinate state of HbNO was observed. HbNO concentration in pentobarbital-anesthetized rats was augmented (change in [HbNO] = 1.6–5.5 μM) by infusion of l-arginine (0.2–0.6 g/kg) but not d-arginine. Using this method, we attempted to evaluate the effects of temocapril on HbNO dynamics in an l-NAME-induced rat endothelial dysfunction model. The oral administration of l-NAME for 2 wk induced a serious hypertension, and the HbNO concentration was reduced (change in [HbNO] = 5.7 μM). Coadministration of temocapril dose dependently improved both changes in blood pressure and the systemic HbNO concentration. In this study, we succeeded in measuring the blood HbNO level as an index of NO by the EPR HbNO signal subtraction method. We also demonstrated that temocapril improves abnormalities of NO dynamics in l-NAME-induced endothelial dysfunction rats using the EPR HbNO signal subtraction method.

A Study of V3+/4+ Levels in Semi-insulating 6H-SiC using Optical Admittance and Electron Paramagnetic Resonance Spectroscopies

2006 ◽  
Vol 911 ◽  
Author(s):  
Wonwoo Lee ◽  
Mary E Zvanut
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Charge State ◽  
Conduction Band ◽  
Epr Spectroscopy ◽  
Admittance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Characteristic Spectrum ◽  
Epr Measurements ◽  
The Individual ◽  
Electron Paramagnetic

AbstractThe purpose of this study is to identify the vanadium acceptor levels in semi-insulating (SI) 6H-SiC using optical admittance spectroscopy (OAS) and electron paramagnetic resonance (EPR) spectroscopy. OAS conductance peaks near at 0.67 ± 0.02 eV and 0.70 ± 0.02 eV are identified as V3+/4+ levels at the quasi-cubic sites. An OAS peak at 0.87 eV is assigned to the same transition at the hexagonal site. EPR measurements before illumination revealed the characteristic spectrum of V3+. The presence of the V3+ signal supports the identification of the OAS peaks as transitions from the V3+/4+ level to the conduction band. Photo-induced EPR measurements reveal a change in the intensity of V3+ and V4+ at 0.8 ± 0.1 eV, where the amplitude of the V3+ charge state decreases and that of V4+ increases by approximately equal amounts. Although the individual sites are not resolved in the photo-induced EPR data, the 0.8 eV feature strongly supports the assignment of the three OAS peaks as acceptor levels.

Spin reorientation transition and spin dynamics study of perovskite orthoferrite TmFeO3 detected by electron paramagnetic resonance

2020 ◽  
Vol 22 (37) ◽  
pp. 21403-21411
Author(s):  
Poorva Sharma ◽  
Jiyu Fan ◽  
Ashwini Kumar ◽  
Arvind Yogi ◽  
Yisheng Chai ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Spin Dynamics ◽  
Spin Reorientation ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Spin Reorientation Transition ◽  
Different Temperatures ◽  
Electron Paramagnetic

(Right) EPR spectrum of TmFeO3 from 20–300 K. (Left) (a) Asymmetry behavior w.r.t. temperature (K), (b) ΔHppvs. T, (c) Plot as ln(ΔHpp × T) vs. 1000/T, (d) DIN (inset represents χdcvs. T at different temperatures).

scholarly journals Concentration of Fe(3+)-Triapine in BEAS-2B Cells

2019 ◽  
Vol 20 (12) ◽  
pp. 3062 ◽  
Author(s):  
William E. Antholine ◽  
Charles R. Myers
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Tumor Cells ◽  
Iron Uptake ◽  
Antitumor Agent ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Epr Method ◽  
First Time ◽  
Electron Paramagnetic ◽  
In Cells

An electron paramagnetic resonance (EPR) method was used to determine the concentration of the antitumor agent Triapine in BEAS-2B cells when Triapine was bound to iron (Fe). Knowledge of the concentration of Fe-Triapine in tumor cells may be useful to adjust the administration of the drug or to adjust iron uptake in tumor cells. An EPR spectrum is obtained for Fe(3+)-Triapine, Fe(3+)(Tp)2+, in BEAS-2B cells after addition of Fe(3+)(Tp)2+. Detection of the low spin signal for Fe(3+)(Tp)2+ shows that the Fe(3+)(Tp)2+ complex is intact in these cells. It is proposed that Triapine acquires iron from transferrin in cells including tumor cells. Here, it is shown that iron from purified Fe-transferrin is transferred to Triapine after the addition of ascorbate. To our knowledge, this is the first time that the EPR method has been used to determine the concentration of an iron antitumor agent in cells.

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